In the evaluation of patients with pulmonary hypertension, the etiology is usually apparent: in most instances, it is acquired or congenital heart disease, pulmonary disease, etc. A small group of cases in which the cause is not readily apparent, however, are usually termed “idiopathic.” Such would have been the diagnosis in a 6-year-old boy seen by the authors if pulmonary arteriography had not been performed. This case, one of stenosis of the pulmonary veins, is therefore reported as an example of the importance of pulmonary arteriography in diagnosing rare and obscure causes of pulmonary hypertension. Moreover, as no good example of the angiocardiographic findings exists in previously reported cases, we were of the opinion that our angiocardiograms would be of further educational value. This 6-year-old boy was admitted to the St. Louis Childrens Hospital, Washington University, St. Louis, Mo., for evaluation of a heart murmur discovered at the time of preschool examination. Except for a Grade 2/6 eject...